There is no AutoCAD system variable to set this, but it is settable using VisualLISP. Here is code that will do that. Variables are not localized, but should be. This is just a quick demonstration of how you can do what you're asking. You can eliminate all those lines that dump objects. That's my way of drilling down to find the right property to set.
;set drawing to south azimuth
(defun c:go()
(vl-load-com)
(getdoc)
(vlax-dump-object dwgstg t)
(setq ambstg (vlax-get-property dwgstg 'AmbientSettings))
(vlax-dump-object ambstg t)
(setq dirstg (vlax-get-property ambstg 'DirectionSettings))
(vlax-dump-object dirstg t)
(setq meastyp (vlax-get-property dirstg 'MeasurementType))
(vlax-dump-object meastyp t)
(vlax-put-property meastyp 'Value 3)
(vlax-dump-object meastyp t)
);end defun
;-----------------------------------getdoc function---------------------------------------
(defun getdoc ()
(setq prod (vlax-product-key))
(setq acadapp (vlax-get-acad-object))
(getaecappnumber)
(setq c3dapp (vla-getinterfaceobject acadapp (strcat "AeccXUiLand.AeccApplication" aecappno)) ;
C3Ddoc (vla-get-activedocument C3Dapp)
c3dstg (vlax-get-property c3ddoc 'Settings)
dwgstg (vlax-get-property c3dstg 'DrawingSettings)
UnZoSetg (vlax-get-property dwgstg 'UnitZoneSettings)
dwgsc (vlax-get-property UnZoSetg 'DrawingScale)
)
;(vlax-dump-object UnZoSetg t)
(princ)
)
;-----------------------------------end getdoc---------------------------------------------
;---------------GETAECAPPNO function----------------------------
(defun getAecAppNumber()
(setq aecappno (cond ((vl-string-search "\\R17.0\\" prod)
".4.0"
)
;;2007
((vl-string-search "\\R17.1\\" prod)
".5.0"
)
;;2008
((vl-string-search "\\R17.2\\" prod)
".6.0"
)
;;2009
((vl-string-search "\\R18.0\\" prod)
".7.0"
)
;;2010
((vl-string-search "\\R18.1\\" prod)
".8.0"
)
;;2011
((vl-string-search "\\R18.2\\" prod)
".9.0"
)
;;2012
((vl-string-search "\\R19.0\\" prod)
".10.0"
)
;;2013
((vl-string-search "\\R19.1\\" prod)
".10.3"
)
;;2014
((vl-string-search "\\R20.0\\" prod)
".10.4"
)
;;2015
((vl-string-search "\\R20.1\\" prod)
".10.5"
)
;;2016
((vl-string-search "\\R21.0\\" prod)
".11.0"
)
;;2017
(t "")
)
)
);end defun
;------------------------------end getaecappno-------------------------------------------------
Tim Corey
MicroCAD Training and Consulting, Inc.
Redding, CA
Autodesk Platinum Reseller
New knowledge is the most valuable commodity on earth. -- Kurt Vonnegut